Development of a cellular biosensor for the detection of aflatoxin B1, based on the interaction of membrane engineered Vero cells with anti-AFB1 antibodies on the surface of gold nanoparticle screen printed electrodes

Impedimetric nanoimmunosensor platform for aflatoxin B1 detection in peanuts

This article developed a novel electrochemical immunosensor for the specific detection of aflatoxin B1 (AFB1). Amino-functionalized iron oxide nanoparticles (Fe₃ O₄ -NH₂ ) were synthesized. Fe₃ O₄ -NH₂ were chemically bound on self-assembly monolayers (SAMs) of mercaptobenzoic acid (MBA). Finally, polyclonal antibodies (pAb) were immobilized on Fe₃ O₄ -NH₂ -MBA. The sensor system was evaluated through atomic force microscopy (AFM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). A reduction in the anodic and cathodic peak currents was observed after the assembly of the sensor platform. The charge transfer resistance (R_ct ) was increased due to the electrically insulating bioconjugates. Then, the specific interaction between the sensor platform and AFB1 blocks the electron transfer of the [Fe(CN)₆ ]^3-/4- redox pair. The nanoimmunosensor showed a linear response range estimated from 0.5 to 30 μg/mL with a limit of detection (LOD) of 9.47 μg/mL and a limit of quantification (LOQ) of 28.72 μg/mL for AFB1 identification in a purified sample. In addition, a LOD of 3.79 μg/mL, a LOQ of 11.48 μg/mL, and a regression coefficient of 0.9891 were estimated for biodetection tests on peanut samples. The proposed immunosensor represents a simple alternative, successfully applied in detecting AFB1 in peanuts, and therefore, represents a valuable tool for ensuring food safety.

Progress in the Development of Detection Strategies Based on Olfactory and Gustatory Biomimetic Biosensors

The biomimetic olfactory and gustatory biosensing devices have broad applications in many fields, such as industry, security, and biomedicine. The development of these biosensors was inspired by the organization of biological olfactory and gustatory systems. In this review, we summarized the most recent advances in the development of detection strategies for chemical sensing based on olfactory and gustatory biomimetic biosensors. First, sensing mechanisms and principles of olfaction and gustation are briefly introduced. Then, different biomimetic sensing detection strategies are outlined based on different sensing devices functionalized with various molecular and cellular components originating from natural olfactory and gustatory systems. Thereafter, various biomimetic olfactory and gustatory biosensors are introduced in detail by classifying and summarizing the detection strategies based on different sensing devices. Finally, the future directions and challenges of biomimetic biosensing development are proposed and discussed.

Development and performance characteristics evaluation of a new Bioelectric Recognition Assay (BERA) method for rapid Sars-CoV-2 detection in clinical samples

Introduction

As the second wave of COVID-19 pandemic is in progress the development of fast and cost-effective approaches for diagnosis is essential. The aim of the present study was to develop and evaluate the performance characteristics of a new Bioelectric Recognition Assay (BERA) regarding Sars-CoV-2 detection in clinical samples and its potential to be used as a point of care test.

Materials and methods

All tests were performed using a custom portable hardware device developed by EMBIO DIAGNOSTICS (EMBIO DIAGNOSTICS Ltd, Cyprus). 110 positive and 136 negative samples tested by RT-PCR were used in order to define the lower limit of detection (L.O.D.) of the system, as well as the sensitivity and the specificity of the method.

Results

The system was able to detect a viral concentration of 4 genome copies/μL. The method displayed total sensitivity of 92.7 % (95 %CI: 86.2–96.8) and 97.8 % specificity (95 %CI: 93.7–99.5). When samples were grouped according to the recorded Ct values the BERA biosensor displayed 100.00 % sensitivity (95 %CI: 84.6–100.0) for Ct values <20−30. For the aforementioned Ct values the Positive Predictive Value (PPV) of the method was estimated at 31.4 % for COVID-19 prevalence of 1% and at 70.5 % for 5% prevalence. At the same time the Negative Predictive Value (NPV) of the BERA biosensor was at 100.0 % for both prevalence rates.

Conclusions

EMBIO DIAGNOSTICS BERA for the detection of SARS-CoV-2 infection has the potential to allow rapid and cost-effective detection and subsequent isolation of confirmed cases, and therefore reduce household and community transmissions.

An Impedance Based Electrochemical Immunosensor for Aflatoxin B1 Monitoring in Pistachio Matrices

Aflatoxins are highly toxic fungal secondary metabolites that often contaminate food and feed commodities. An electrochemical immunosensor for the determination of aflatoxin B1 (AFB1) was fabricated by immobilizing monoclonal AFB1 antibodies onto a screen-printed gold electrode that was modified with carbo-methyldextran by N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide cross-linking. An electrochemical interfacial modelling of biomolecular recognition was suggested and reasonably interpreted. Impedance technology was employed for the quantitative determination of AFB1. The limit of detection concentration of AFB1 for standard solutions and spiked pistachio samples was 0.5 ng/mL and 1 ng/mL, respectively. The immunosensor was able to successfully determine AFB1 concentrations in the range of 4.56–50.86 ng/mL in unknown pistachio samples. Comparative chromatographic analysis revealed that AFB1 concentrations that were higher than 345 ng/mL were not within the immunosensor’s upper limits of detection. Selectivity studies against Ochratoxin A and Aflatoxin M1 demonstrated that the proposed AFB1 immunosensor was able to differentiate between these other fungal mycotoxins. The novel electrochemical immunosensor approach has the potential for rapid sample screening in a portable, disposable format, thus contributing to the requirement for effective prevention and the control of aflatoxin B1 in pistachios.

Development of a Portable, Ultra-Rapid and Ultra-Sensitive Cell-Based Biosensor for the Direct Detection of the SARS-CoV-2 S1 Spike Protein Antigen

One of the key challenges of the recent COVID-19 pandemic is the ability to accurately estimate the number of infected individuals, particularly asymptomatic and/or early-stage patients. We herewith report the proof-of-concept development of a biosensor able to detect the SARS-CoV-2 S1 spike protein expressed on the surface of the virus. The biosensor is based on membrane-engineered mammalian cells bearing the human chimeric spike S1 antibody. We demonstrate that the attachment of the protein to the membrane-bound antibodies resulted in a selective and considerable change in the cellular bioelectric properties measured by means of a Bioelectric Recognition Assay. The novel biosensor provided results in an ultra-rapid manner (3 min), with a detection limit of 1 fg/mL and a semi-linear range of response between 10 fg and 1 μg/mL. In addition, no cross-reactivity was observed against the SARS-CoV-2 nucleocapsid protein. Furthermore, the biosensor was configured as a ready-to-use platform, including a portable read-out device operated via smartphone/tablet. In this way, we demonstrate that the novel biosensor can be potentially applied for the mass screening of SARS-CoV-2 surface antigens without prior sample processing, therefore offering a possible solution for the timely monitoring and eventual control of the global coronavirus pandemic.

Development of a flexible, sweat-based neuropeptide Y detection platform

Neuropeptide Y (NPY) biomarker levels have a close association with the diagnosis of Major Depression Disorder (MDD) and anxiety disorders. Quantifying NPY in correlation to self-reported symptoms will be an important measure to ensure a relatively uniform diagnosis and help with disease prognosis of these disorders. The work presented is a novel, passive eccrine sweat based, electrochemical detection platform for quantification of NPY biomarker levels. The paper offers a comparison between non-porous and porous sensor platforms using various electrochemical detection techniques. This work uses a novel strategy towards designing an optimal nanobioelectronic interface to measure NPY. The portability aspect of this detection platform is discussed by the demonstration a novel, portable EmStat Pico based electronic platform. The detection limit of the sensor is 10 pg mL⁻¹ and its range is 20–500 pg mL⁻¹. The NPY detection platform is envisioned to be a wearable point-of need monitoring system for management of chronic anxiety disorders and MDD.

Novel wearable NPY biomarker tracking system, envisioned to be a chronic anxiety and MDD management platform via self-monitoring.

Bioelectronic tongue: Current status and perspectives

In the course of evolution, nature has endowed humans with systems for the recognition of a wide range of tastes with a sensitivity and selectivity which are indispensable for the evaluation of edibility and flavour attributes. Inspiration by a biological sense of taste has become a basis for the design of instruments, operation principles and parameters enabling to mimic the unique properties of their biological precursors. In response to the demand for fast, sensitive and selective techniques of flavouring analysis, devices belonging to the group of bioelectronic tongues (B-ETs) have been designed. They combine achievements of chemometric analysis employed for many years in electronic tongues (ETs), with unique properties of bio-inspired materials, such as natural taste receptors (TRs) regarding receptor/ligand affinity. Investigations of the efficiency of the prototype devices create new application possibilities and suggest successful implementation in real applications. With advances in the field of biotechnology, microfluidics and nanotechnologies, many exciting developments have been made in the design of B-ETs in the last five years or so. The presented characteristics of the recent design solutions, application possibilities, critical evaluation of potentialities and limitations as well as the outline of further development prospects related to B-ETs should contribute to the systematisation and expansion of our knowledge.

Analysis of musts and wines by means of a bio-electronic tongue based on tyrosinase and glucose oxidase using polypyrrole/gold nanoparticles as the electron mediator

A bioelectronic tongue (bioET) based on combinations of enzymes (tyrosinase and glucose oxidase) and polypyrrole (Ppy) or polypyrrole/AuNP (Ppy/AuNP) composites was build up and applied to the analysis and discrimination of musts and wines. Voltammetric responses of the array of sensors demonstrated the effectiveness of polymers as electron mediators and the existence of favorable synergistic effects between Ppy and the AuNPs. Using Principal Component Analysis and Parallel Factor Analysis it was possible to discriminate musts according to the °Brix and TPI (Total Polyphenol Index), and wines according to the alcoholic degree and TPI. Partial Least Squares provided good correlations between the bioET output and traditional chemical parameters. Moreover, Support Vector Machines permitted to predict the TPI and the alcoholic degree of wines, from data provided by the bioET in the corresponding grapes. This result opens the possibility to predict wine characteristics from the beginning of the vinification process.

An Ultra-Rapid Biosensory Point-of-Care (POC) Assay for Prostate-Specific Antigen (PSA) Detection in Human Serum

Prostate-specific antigen (PSA) is the established routine screening tool for the detection of early-stage prostate cancer. Given the laboratory-centric nature of the process, the development of a portable, ultra rapid high-throughput system for PSA screening is highly desirable. In this study, an advancedpoint-of-care system for PSA detection in human serum was developed based on a cellular biosensor where the cell membrane was modified by electroinserting a specific antibody against PSA. Thirty nine human serum samples were used for validation of this biosensory system for PSA detection. Samples were analyzed in parallel with a standard immunoradiometric assay (IRMA) and an established electrochemical immunoassay was used for comparison purposes. They were classified in three different PSA concentration ranges (0, <4 and ≥4 ng/mL). Cells membrane-engineered with 0.25 μg/mL anti-PSA antibody demonstrated a statistically lower response against the upper (≥4 ng/mL) PSA concentration range. In addition, the cell-based biosensor performed better than the immunosensor in terms of sensitivity and resolution against positive samples containing <4 ng/mL PSA. In spite of its preliminary, proof-of-concept stage of development, the cell-based biosensor could be used as aninitiative for the development of a fast, low-cost, and high-throughput POC screening system for PSA.

Recent progress on cell-based biosensors for analysis of food safety and quality control

Food quality and safety has become a subject of major concern for authorities and professionals in the food supply chain. Rapid methods, particularly biosensors, have exceptional specificity and sensitivity, rapid response times, low cost, relatively compact size, and are user friendly to operate. Cell-based biosensors are portable, and provide the biological activity of the analyte suitable for an initial screening of food. In this overview, the utilization of cell-based biosensors for food safety and quality analyses, such as detecting toxins, foodborne pathogens, allergens, and evaluating toxicity and function are summarized. Our results will promote the future development of cell-based biosensors in the food field.

The Simultaneous Voltammetric Determination of Aflatoxins В1 and М1 on a Glassy-Carbon Electrode

For the first time, the possibility of using stripping voltammetry for the simultaneous determination of aflatoxins В1 and М1 on a glassy-carbon electrode has been shown. The influence of various factors (Еэ, τэ, w, and the nature of the background electrolyte) on the potential and magnitude of the oxidation current of mycotoxins has been estimated. Working conditions for voltammetric determination and reproducibility of analytical signals for two mycotoxins have been selected. The mutual influence of aflatoxins В1 and М1 on the value of analytical signals in their simultaneous presence has been studied. It has been found that, in the range of their detectable contents, the presence of aflatoxin В1 reduces the analytical signal of aflatoxin М1 by 45-50%, but the linearity of the calibration dependence is preserved. The content of aflatoxin М1 in determination of aflatoxin B1 does not exert a significant effect in the range of 10-15%. Based on the results obtained, a procedure has been proposed for determining the content of aflatoxins В1 and М1 in their joint presence in milk by voltammetry in the concentration ranges 2 × 10-3 ÷ 2 × 10-1 mg/dm3 and 2 × 10-4 ÷ 2 × 10-2 mg/dm3, respectively (Sr not more than 18%).